Conventionally, to increase a turning characteristic, various four-wheel steering devices for controlling steering angles of rear wheels are proposed. For example, at a low traveling speed, making a turning angle of front wheels and steering angle of rear wheels antiphase can reduce a minimum turning radius. At a high traveling speed, to increase controllability in lane changing by making a turning angle of front wheels and a steering angle of rear wheels in phase. In addition, as a technology of independently controlling toe angles of left and right rear wheels, there are provided technologies in which an actuator uses a hydraulic mechanism, and an actuator uses a lead screw mechanism in place of the hydraulic mechanism (for example, FIGS. 1 to 6 of Patent Document 1).
Patent Document 2 discloses a technology in which a steering motor is installed to control variation in a direction of turning wheels (front wheels), and a controller controls a steering motor on the basis of information of a steering angle from a steering wheel to be operated by a driver. According to the steering device, even when a driver changes a steering angle direction in such a state that an actual turning angle of turning wheels has a response delay to a steering angle target of front wheels according to steering by a driver, it is prevented that a corresponding relationship between the actual steering angle of the front wheels and a steering direction of the vehicle in response to the actual turning angle of the front wheels becomes reverse by reflecting an actual turning angle measured at that timing in a turning angle target value.